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Q&A: Do I Need Energy Gels for a Half-Marathon?

Do I need energy gels for a half-marathon? Does it depend on my pace, or how long I’ll be running? Is a pre-race meal more important?

Energy gels are primarily a source of carbohydrates (carbs), one of the three main nutrients endurance athletes need during prolonged activity, in addition to fluid and electrolytes. Carbs are our muscles’ (and brain’s) primary source of fuel, much like gas in a car. And to continue to the car metaphor, our bodies can store a certain amount of gas in our tank (muscles and liver), called glycogen.

If we perform an activity long enough and our gas tank runs out, then the engine stops running and we experience the dreaded “bonk.” To slow the depletion of our internal fuel stores (glycogen), we can consume external sources of carbs, such as sports drinks or energy gels.

Whether and how much external carbs we need depends on a number of factors including:

  • Running pace: Running faster burns fuel from our tank relatively faster than a slower pace
  • Duration of the run
  • Metabolic (fuel) efficiency: Depending on training and fueling habits, people may be able to tap more into fat as a fuel at certain paces. Metabolic testing can help determine this info.
  • Environment: Heat and humidity make us burn more fuel, just like when we use the A/C in our car during a hot summer day
  • Size and fullness of your “gas tank”

Most people starting a half-marathon on a full tank (i.e. well-fed with adequate pre-race meals in the preceding 24 hours), and adequately hydrated should be able to complete the race in moderate weather without needing external carbohydrate stores. However, certain cases where it could be helpful to have a gel or similar source of carb available during a race include:

  • During periods of caloric restriction or heavy training, where you may be starting the race without a full tank
  • Abnormally hot or humid conditions
  • Attempting to run at a pace significantly faster than what you’ve trained at
  • Dealing with the potential for mental fatigue: Studies have shown that just swishing a little bit of sports drink, gel, or other source of simple carbohydrates in your mouth can trigger receptors in your brain that make the perception of effort of an activity lower. In other words, it makes running a half-marathon feel less arduous.

If you have a sensitive stomach and want to minimize the risk of gastrointestinal distress, try to plan to have half the energy gel around a water break, and consume a source of fluid (about four to six gulps of water) within a few minutes of eating the gel.


Jason Machowsky

Jason Machowsky is a board-certified sports dietitian and certified strength and conditioning specialist at the Tisch Sports Performance Center at Hospital for Special Surgery. In addition to working with a variety of endurance athletes, he serves our nation’s athletes as an active member of the United States Olympic Committee Sports Dietitian Registry. Jason has written a number of Ask the Expert articles for the New York Road Runners, in addition to speaking at the TCS New York City Marathon Expo, the United Airlines NYC Half Experience, and the NYRR Learning Series. He received his Master of Science degree in applied physiology and nutrition from Teachers College at Columbia University.

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